Code Quality: Global usings, single line namespaces

Description

I think we should start the conversation about global usings and single line namespace declarations.

_Originally posted by @lukeblevins in https://github.com/files-community/Files/issues/11832#issuecomment-1484257518_

Concerned code

All cs files

Gains

Better readability

Requirements

• Agree upon a subset of using statements that are common to most source files
• Add GlobalUsings.cs
• Amend code quality guidelines for single line namespace definitions
• Implement single line namespace defs

Comments

This is under discussion on the discord server

[0x5bfa]

Here’s my proposal

// System
global using global::System;
global using global::System.Collections.Generic;
global using global::System.Collections.ObjectModel;
global using global::System.Linq;
global using global::System.Text;
global using global::System.Threading;
global using global::System.Threading.Tasks;

// Windows Community Toolkit
global using global::CommunityToolkit.Mvvm.ComponentModel;
global using global::CommunityToolkit.Mvvm.Input;
global using global::CommunityToolkit.Mvvm.Messaging;

// Files Front-end
global using global::Files.App.Helpers;
global using global::Files.App.Extensions;
global using global::Files.App.Filesystem;
// NOTE: We can add more here...

// Files Back-end
global using global::Files.Shared;
global using global::Files.App.Storage;
global using global::Files.Sdk.Storage;
// NOTE: We can add more here...

// Vanara
// NOTE: We can add more here...

[yaira2]

@0x5bfa we can definitely do that but let’s keep it separate from the Global Usings PR.